Expression of hybrid Ia molecules on the cell surface of reticulum cell sarcomas that are undetectable on host SJL/J lymphocytes

A spontaneous sarcoma dependent on host tumor-specific immune lymphocytes

The immune surveillance theory postulates that spontaneous tumors are normally rejected by the immune system and appear only when they override host-immune recognition and rejection mechanisms. The present mini-review describes a spontaneous tumor system, the reticulum cell sarcomas (RCS) in SJL/J mice, that is dependent on host tumor-specific immune lymphocytes for growth. This continuous tumor-specific response results in tumor progression and death of the host. This tumor system contradicts the basic concept of immune surveillance. We propose as an explanation that some highly antigenic tumors, like the RCS, may have evolved in a non-autonomous fashion but, nevertheless, have lost regulatory controls of cell proliferation. In the RCS system, the tumor expresses Class II MHC I-E like specificities that are not expressed on the host cells and which selectively stimulate a subpopulation of I-E specific T cells, the V beta 17 a+ clonotype, leading to their expansion and continuous nurturing of the tumor via secreted lymphokines. This neoantigenic stimulation bypasses the tumor regulatory response that might have resulted if the tumor had not expressed neoantigens. Furthermore, passive administration of anti-clonotypic antibody to tumor-bearing mice results in tumor regression and long-term survival through removal of the tumor reactive T cells. Thus, in this tumor system, immunosuppressive treatments are the prescription for tumor rejection.

Role of MHC, Mls and TCR in immune tolerance

MHC class II molecules and self antigens, such as Mls, influence T-cell selection by clonal deletion of potentially self-reactive T cells. In order to examine the role of various class II molecules in the T-cell receptor-self antigen interaction, class II transgenic and recombinant mice were analysed for TCR expression. Our studies indicate that the A alpha and E alpha chains can present Mls gene products for the clonal deletion of V beta 6-bearing T cells, and that the A alpha q chain is defective in this process. We have also shown that E alpha A beta heterodimer in transgenic and recombinant mice is expressed and functions to delete I-E reactive V beta llT cells, demonstrating again the role of the E alpha molecule.

Age-related changes in the morphology and immunophenotype of spontaneous lymphomas of SJL/N mice

Forty-four SJL mice were killed at intervals to follow the spontaneous development of lymphomas. These were detected in 28 of 38 mice aged 24 weeks or more. Immunoperoxidase stains were applied on cryostat sections of lymphomas from various sites (spleen, mesenteric lymph nodes, Peyer's patches, and other lymph nodes), sampled from 19 mice of different age groups, to study tumour immunophenotype in correlation with histological features. With a panel of antibodies against Thy 1.2, Lyt 1, and Lyt 2, and the mouse immunoglobulin heavy and light chains, all the 19 tumours were shown to be B-cell derived. This was further supported by the detection of Ia antigens on the tumour cells. Six mice had plasmacytoid or predominantly plasmacytoid tumours expressing gamma kappa. Three mice had mixed plasmacytoid and pleomorphic tumours which also showed gamma kappa positivity. The ages of these nine mice ranged from 24 to 44 weeks with a median of 36 weeks. Pleomorphic tumours were found in ten mice (age range = 36-52 weeks, median = 44 weeks). These tumours were more heterogeneous, expressing either alpha, mu, or gamma, or with loss of heavy chain expression altogether. These age-related changes are probably a sign of progressive loss of differentiation in B lymphomas.

The SJL/J T cell response to both spontaneous and transplantable syngeneic reticulum cell sarcoma is mediated predominantly by the V beta 17a+ T cell clonotype

Previous studies have revealed that the reticulum cell sarcoma (RCS) of SJL/J (H-2s, IE-) mice express an "IE-like" stimulatory tumor-associated antigen, the expression of which is requisite for stimulating host T cells necessary for tumor growth. Herein, we present evidence that the predominant T cells raised in the syngeneic response to both spontaneous and transplantable RCS tumors are of the V beta 17a TCR clonotype. The V beta 17a+ clonotype of T cells has been shown to interact with IE allogeneic specificities. We demonstrate that all four characterized RCS-specific T cell hybridomas stained positively for the anti-V beta 17a mAb, KJ23a. Additionally, KJ23a, when added to cocultures of the T cell hybridomas and RCS tumors, inhibited the release of IL-2 by the hybridomas. Further, KJ23a was shown to markedly inhibit the proliferation of SJL/J T cells when cocultured with either spontaneous or transplantable RCS tumor cells. When analyzed by flow cytometry, the T cell blast population raised in response to both spontaneous and transplantable RCS were greater than 80% KJ23a+. These T cells were brightly stained by the anti-CD4 mAb, Gk1.5, and, therefore, represent class II-responsive T cells. In corroboration of the in vitro data, T cells derived from mesenteric lymph nodes of RCS tumor-bearing mice had likewise undergone a similar expansion of V beta 17a+, CD4+ T cells. Together, these results indicate that KJ23a+ T cells play an important and predominant role in the response of SJL/J mice to spontaneous RCS tumors and provide further suggestive evidence that the stimulatory antigen(s) on the RCS tumor is IE or an "IE-like" molecule. Significantly, the important role V beta 17a+ T cells play in the response to RCS suggests a potential therapeutic role for KJ23a mAb in the intervention and prevention of RCS tumors in SJL/J mice.

Lymphoid cell populations in splenectomized and nonsplenectomized SJL/J mice bearing Hodgkin's disease-like reticulum cell sarcoma

Using the reticulum cell sarcoma (RCS) of the SJL/J mouse as a model for Hodgkin's disease, the effects of tumor growth and splenectomy on the T-cell and B-cell populations were evaluated. Although splenectomy improved survival and reduced gross observable tumor growth in secondary tumor sites, no effect on T-cell and B-cell populations was detected. We conclude that tumor growth appears to be undetected by the immune system; previously reported immunosuppression in RCS-bearing mice must be due to functional changes and not cell population changes; and splenectomy contributes to survival and suppression of tumor cell growth in secondary sites.

Proliferative responses of T cells from SJL----F1 and F1----SJL bone marrow chimeras to SJL lymphoma cells

RCS tumor cells induce marked proliferation of syngeneic SJL T cells in vivo and in vitro. Certain F1 hybrids of SJL mice give high proliferative responses to gamma-RCS, while other F1 hybrids give low responses. SJL----"non-responder" F1 and "non-responder" F1----SJL semiallogeneic bone marrow chimeras were prepared to study how the host environment affects the ability of T cells to give a proliferative response to gamma-RCS. The results indicate that T cells educated in an SJL host become responsive to RCS cells, while T cells educated in an (SJL X BALB/c)F1 host become unresponsive. This finding applies to both thymus and lymph node T cells. The unresponsiveness in F1 mice is not due to suppressor cells, since added F1 cells do not affect the proliferative response of SJL cells to gamma-RCS. Instead, it appears that RCS-specific T cells are either deleted in (SJL X BALB/c)F1 mice, or expanded in SJL mice as they develop. These findings are discussed in relation to the specificity of the responding T cells, for LPS activated syngeneic B cell blasts as well as RCS cells, and to the presence of a "leaky" thymus barrier in SJL mice for B cells.

Induced type-B reticulum cell neoplasia of CBA mice. II. Functional similarities between tumorigenic reticulum cells and normal accessory cells

In a previous report, it was proposed on the basis of phenotypic evidence that the population of transplantable cells which constituted the major component of experimentally induced type-B reticulum cell neoplasms of CBA strain mice could be a neoplastic counterpart of lymphoid dendritic or veiled accessory cells. This has been further tested by an in vitro examination of their accessory function. Both similarities and differences in behaviour between the neoplastic cells and accessory cells prepared from spleens of normal mice were found. The possible significance of these properties is discussed in relation to the process of neoplastic change.

Identification of hairy cell leukemia subset defining p35 as the human homologue of Ii

A molecule defining a subset of patients with hairy cell leukemia (HCL) on the basis of being abundantly labeled with [35S]methionine, was demonstrated to be the human homologue of murine Ii, a glycoprotein which lacks alloantigenic variation and is associated non-covalently with Ia antigens. In one-dimensional SDS-polyacrylamide gradient gel electrophoresis, the HCL-subset-defining molecule migrated with HLA-DR molecules which were immunoprecipitated with a specific heteroantiserum. These molecules were further defined in two-dimensional, SDS and non-equilibrium pH gradient electrophoresis of either membrane preparations or immunoprecipitates formed with various antibodies. [35S]methionine-labeling of the HCL-subset-defining molecule was greater in hairy leukemic cells than in lymphoblastoid cell lines. The subset-defining species was associated non-covalently with HLA-DR alpha and beta chains and ran electrophoretically at a position described for murine and human Ii molecules (in terms of pI and weight). Metabolic labeling of HLA-A,-B and -DR was also increased in HCL cells relative to lymphoblastoid cell lines. A separate protein, of 41,000 mol. wt and pI of 7-8, resembled another Ii-associated molecule which has been described in murine and human studies.

Experimental models of lymphoproliferative disease. The mouse as a model for human non-Hodgkin's lymphomas and related leukemias

The present review focuses on the mouse as an experimental immunopathologic model for human non-Hodgkin's lymphomas and related leukemias. Immunomorphologic evidence is presented that clearly demonstrates that B- and T-cell subtypes of mouse (murine) lymphoma/leukemia closely resemble and are analogous to B- and T-cell subtypes of human lymphoma/leukemia as defined by recently proposed immunomorphologic classifications. Further evidence is presented that favors the hypothesis that certain types of murine and human B-cell lymphoma develop out of prodromal, prelymphomatous states, which exhibit antecedent morphologic and immunologic abnormalities. The many experimental advantages of the murine systems are stressed, as well as the concept that the presently defined immunomorphologic approach should be effectively combined with molecular and cytogenetic parameters.

HLA and susceptibility to Hodgkin's disease

Strong arguments supporting a genetic linkage between susceptibility to HD and HLA are reported. These observations are based on data from 33 multiplex case families, gathered from international series and from our own studies. They confirm the disturbed segregation of HLA haplotypes among pairs of affected siblings (P less than 0.0005). An excess of a shared haplotype among first cousin pairs of patients is also observed (P less than 0.05). When both sib pairs and cousins are taken together, the segregation distortion is even greater (P less than 0.0002). Although the excess of HLA-identical affected sib pairs would favor a recessive mode of transmission of the disease, the lod score analyses do not allow one to conclude a simple genetic pattern. A two-gene model, based on epistatic cooperation, is discussed and could fit with an intermediate mode of transmission. The review of population data confirms the generally admitted trend of higher susceptibility borne by HLA-A1. There are converging arguments in favor of the prevalence of A1, B5, B18 in HD, and in particular A1 in the mixed cellularity form, while the haplotype, A1, B8, predominant in long survivors seems to possess a protective effect. It is expected that more data from multiplex families and prospective series of unrelated patients, fully HLA typed, may help to bring about a better understanding of the first reported HLA linkage with malignancy.

Properties of reticulum cell sarcomas in SJL/J mice. VIII. Prominent role of RCS cell I-A antigens in the stimulation of syngeneic T cells

While T cells from SJL and from F1 hybrids of SJL that do not express I-E antigens give strong proliferative responses to RCS, T cells from F1 hybrids expressing surface I-E do not. The nature of the stimulating antigen on the RCS cell surface was examined using monoclonal antibodies. Complete inhibition of the T-cell proliferative response was obtained with antibodies to I-A antigens, whereas antibodies to I-E antigens did not inhibit at all. This inhibition was mediated via an effect of the antibodies on the stimulating cells. Biochemical characterization of immunoprecipitated 125I-and 35S-labeled RCS antigens was performed using two-dimensional gel electrophoresis. Using this technique, I-A antigens were readily detected. However, neither Ia.7-specific antibodies nor antibodies specific for E alpha: E beta complexes precipitated any E alpha or E beta chains. Comparison of I-A antigens from RCS and normal SJL spleen cells revealed minor mobility differences in the gels, possibly due to differences in glycosylation, the significance of which needs to be further evaluated. Examination of RNA extracted from RCS, using E alpha and A alpha cDNA probes showed that RCS cells do not transcribe the E alpha gene as has been shown previously for normal H-2s cells. Furthermore, DNA from RCS cells showed a defect in the E alpha gene similar to that known to exist in normal H-2s cells. Our findings exclude the presence of E alpha on RCS cells and suggest a major role for I-A, either alone or in conjunction with another as yet unidentified cell surface antigen, in the stimulation of T cells.